the fuselage. The wing's relative shortness and straightness enabled the lengthy aerial for the primary reconnaissance sensor, the Red Drover X-band radar, to be contained within the fuselage, as the wing provided little obstruction and therefore little interference with the radar. A total of four Armstrong-Siddeley P.156 engines, mounted two apiece in an over-under arrangement of pods positioned at the extreme tips of the wings, provided propulsion. The engine nacelles included variable-geometry air intakes while the engines themselves were equipped with convergent-divergent nozzles. Alternative arrangements of two or three shock cones could have been installed on the nacelles. The aircraft adopted an atypical tail-first configuration; this approach had the effect of greatly reducing trim-drag while also generating increased lift at slower speeds. Longitudinal control was provided by the nose-mounted tail plane via trailing edge elevators, lateral control was enacted by ailerons located on the wing's trailing edge, and directional control was achieved by a conventional rudder. All four of the primary flight control surfaces were actuated by a quadruple-redundant electro-hydraulic control unit, designed by Boulton Paul. Fly-by-wire electrical controls and automatic control systems were also to be employed on the type. The undercarriage, designed by Dowty Group, used an arrangement of a single centre-fuselage main unit complete with four wheels, a nose unit with two wheels, and a pair of outriggers located on the engine nacelles. The Avro 730 lacked a conventional canopy in order to maintain the fineness ratio, the cockpit featured only two small windows facing to the side. On the intended initial development models, a raised canopy would have been present for direct vision; however, production aircraft would have made sole use of an electrically operated retractable periscope in order to provide an external view, including during take-off and landing. As originally envisioned, a crew of three would be carried: pilot, navigator and radar operator. All three were to be contained within the same compartment, which was both pressurised and refrigerated for passenger comfort; lightweight ejection seats were to be provisioned for all crew members. Due to features such as the automatic flight controls and stabilisation systems, the pilot was intended to be capable of supervising some of the aircraft's engineering functions as well, such as the control system, cooling and fuel systems. Cooling was a critical issue for the Avro 730; at Mach 2, the external skin was anticipated to reach 190 °C, this would rise